DESCRIPTION (Directly taken from the application) The gross mortality of patients in the United States (U.S.) with end- stage renal disease (ESRD) treated by hemodialysis (HD) has increased over the past decade. Patients treated by HD have a life expectancy of only 20 percent of the general population at the current mortality rate. The variables associated with morbidity and mortality must include those which are treatment related (amount of dialysis delivered, membrane type) and those which are patient related (age, gender, comorbid illness), yet these variables have not been prospectively evaluated in a large population. The goal of this project is to conduct a prospective, multi-center, randomized clinical trial which will examine the impact of different levels of dialysis dose and membrane composition upon the mortality and morbidity of HD patients. The experimental design is a two-by-two factorial study. Following a series of screening tests, including assessing the ability of delivering the high dose level of dialysis to each prospective participant, participants will be randomized to receive one of two levels of dialysis as measured by 2- pool variable volume KT/V: 0.95 vs 1.4, and to be dialyzed against either low flux cellulosic membranes or high flux synthetic or semisynthetic membranes. Mortality in each of the four groups will be the primary outcome. A series of secondary outcomes including hospitalization frequency, assessment of infectious and cardiac complications, nutritional and general health and morbidity assessment will also be evaluated. Stop points include inadequate dialysis, adverse reaction to the dialysis membrane, transplantation and conclusion of the follow-up period.